1. Field of Invention:
This invention relates to diesel engines and, in particular, to a control system for turbocharged diesel engines.
2. Brief Statement of Prior Art:
A common cause of damage and excessive wear of internal combustion engines results from excessive combustion temperatures in the engine. The operational temperature of the engine can rapidly exceed a safe operational limit by improper operation where the engine is overloaded at any speed, requiring overthrottling and an excessive rate of fuel injection. This often occurs when driving a diesel-powered vehicle into unnoticed head or side winds or climbing unnoticed grades, or failing to notice changes in ambient pressure resulting from altitude changes or high ambient tempertures. Additionally, malfunctions in the engine and its accessory equipment such as in the fuel supply system or fuel injectors, improper timing, turbocharger, restricted air cleaner, leak in a cross over tube, etc. can also cause an improper supply of fuel to the engine and result in an excessive operational temperature of the engine.
When the temperature of an engine exceeds a safe operational temperature, even for periods of relatively short duration, the damage that can be expected includes burned valves, head gasket failures, engine block distortion, cracked manifold and cylinder heads, burning and scoring of pistons, carbon deposits behind piston rings and on injector tips, piston ring failure with resultant high oil consumption and blow by, lubrication oil dilution, cracks in the turbocharger unit and expansion of aluminum pistons resulting in aluminum deposits on cylinder walls and piston sizure.
It is generally recognized that the engine temperature of a diesel engine is critically affected by the aforementioned operational or equipment defects. As a result, many diesel engines are provided with pyrometers to monitor the exhaust gas temperature of the engine. Some of the pyrometers have been equipped with visual or audible warning signal generators to alert the operator when the exhaust gas temperature exceeds a predetermined, safe operational level. These devices are not entirely satisfactory since the warning signals can be inadvertently or deliberately ignored during operation of the engine. Since operations of relatively short durations at excessive temperatures can have disastrous effects on the engine, any failure to take corrective steps immediately upon indication of an excessive exhaust gas temperature, can result in an expensive and time consuming engine overhaul. Unmanned engines present similar problems.
In our prior patent, we disclosed and claimed a control system for a conventional, normally aspirated diesel engine using a controlled fuel by-pass. There is also disclosed in U.S. Pat. No. 3,605,711 a hydraulic control system which adjusts the position of a fuel rack in an on-off, non-proportional manner. None of these prior systems are particularly adaptable to pressurized induction engines such as turbocharged engines.